[Antennas] Antenna SWR

Tue Mar 1 18:08:49 EST 2011

Remember, a "perfect" vertical should have about 35 ohms resistive at resonance, so the SWR will NOT be 1:1, but rather about 1.4:1. If the antenna is tuned to 50 ohm resistive over dry ground, then the ground gets wet (and thus "better") then SWR will climb a little (up to that 1.4:1). The test would be to check the "X" component and see if it's going low. 35 Ohms is the "correct" error - but remember 1.4:1 is also possible at 70 ohms - but that would not be logical. Rather it would be a sign of some other problem (like water ingress).
73,
Jay
AD5PE
--- On Tue, 3/1/11, Don Keith <n4kc at bellsouth.net> wrote:
> From: Don Keith <n4kc at bellsouth.net>
> Subject: [Antennas] Antenna SWR
> To: Antennas at mailman.qth.net
> Date: Tuesday, March 1, 2011, 9:54 PM
> Same phenomenon that baffles many
> first-time vertical builders.  The more radials--the better
> the ground plane--the more the SWR creeps up.  Many just
> drive a ground rod into the ground since the SWR is better,
> happily assuming that is the best and most efficient antenna
> they can get.  Or settle for a couple of ground radials
> because SWR rises as they add more.
>  
> I suspect your ground plane is better after the rain.  If
> the SWR didn't get above 2:1, I would not even worry about
> it...other than increase the number of radials if you can.
>  
> 73,
>  
> Don N4KC
> www.n4kc.com
> www.donkeith.com
>  
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